Description

add get_context_data to ModelAdmin/AdminSite

it's useful have a common place where configure common context variables ( as in class based view ).
Both ModelAdmin/AdminSite have no similar method, and you are forced to override all the views to put a
common object into the context (context processor is not a good solution because is involved also in non-admin's views).

The patch simply add get_context_data(**kwargs) to ModelAdmin/AdminSite and change lines like